Display device

ABSTRACT

The present disclosure provides a display device including a display panel, an optical layer, and a cover layer. The display panel has a substrate with two opposite first edges. The optical layer is disposed on the display panel, and the optical layer has two opposite second edges corresponding to the two opposite first edges respectively. The cover layer is disposed on the optical layer. One of the two opposite first edges and one of the two opposite second edges corresponding to the one of the two opposite first edges are not aligned.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 17/739,182, filed on May 9, 2022, which is a continuationapplication of U.S. application Ser. No. 16/916,074, filed on Jun. 29,2020, which is a continuation application of U.S. application Ser. No.16/442,574, filed on Jun. 17, 2019, which is a continuation applicationof U.S. application Ser. No. 15/921,677, filed on Mar. 15, 2018. Thecontents of these applications are incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

The present disclosure relates to a display device, and moreparticularly to a foldable display device.

2. Description of the Prior Art

In recent years, foldable display design has become one of nextgeneration technologies. A foldable display device means the device canbe curved, folded, stretched, flexed, or the like (generally referred toas “foldable” hereinafter), so the foldable display device offersportability when in a folded state and expands into a relatively largesized display when in an unfolded state. Accordingly, the foldabledisplay device may have various applications in electronic displays usedin televisions, monitors, mobile computing devices, such as smartphones,tablet computers, mobile personal computers (PCs), and electronic bookreaders, and wearable devices, such as smart watches. However, the morethe number of the stacked layers or films of the display device is, themore complicated the stresses among the display device when the displaydevice is in the folded state or a bent state, which will limit thefolding or bending angle of the display device, or damage the layers orfilms of the display device. Thus, it's still in need of facilitatingfolding or bending of the display device and mitigating damage to theelements in the display device.

SUMMARY OF THE DISCLOSURE

The present disclosure provides a display device including a displaypanel, an optical layer, and a cover layer. The display panel has asubstrate with two opposite first edges. The optical layer is disposedon the display panel, and the optical layer has two opposite secondedges corresponding to the two opposite first edges respectively. Thecover layer is disposed on the optical layer. One of the two oppositefirst edges and one of the two opposite second edges corresponding tothe one of the two opposite first edges are not aligned.

These and other objectives of the present disclosure will no doubtbecome obvious to those of ordinary skill in the art after reading thefollowing detailed description of the embodiment that is illustrated inthe various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a cross-sectional view of a displaydevice according to a first embodiment of the present disclosure.

FIG. 2 schematically illustrates the display device in a folded state.

FIG. 3 schematically illustrates a method of forming the cover layer.

FIG. 4 schematically illustrates a top view of a display deviceaccording to a second embodiment of the present disclosure.

FIG. 5 schematically illustrates a cross-sectional view of the displaydevice taken along a cross-sectional line A-A′ of FIG. 4 .

FIG. 6 schematically illustrates a display device according to a thirdembodiment of the present disclosure.

FIG. 7 schematically illustrates a display device according to a fourthembodiment of the present disclosure.

FIG. 8 schematically illustrates a display device according to a fifthembodiment of the present disclosure.

FIG. 9 schematically illustrates a display device according to a sixthembodiment of the present disclosure.

FIG. 10 schematically illustrates a display device according to aseventh embodiment of the present disclosure.

FIG. 11 schematically illustrates a display device according to aneighth embodiment of the present disclosure.

FIG. 12 schematically illustrates a display device according to a ninthembodiment of the present disclosure.

DETAILED DESCRIPTION

The present disclosure may be understood by reference to the followingdetailed description, taken in conjunction with the drawings asdescribed below. It is noted that, for purposes of illustrative clarityand being easily understood by the readers, various drawings of thisdisclosure show a portion of the display device, and certain elements invarious drawings may not be drawn to scale. In addition, the number anddimension of each device shown in drawings are only illustrative and arenot intended to limit the scope of the present disclosure.

Certain terms are used throughout the description and following claimsto refer to particular components. As one skilled in the art willunderstand, electronic equipment manufacturers may refer to a componentby different names. This document does not intend to distinguish betweencomponents that differ in name but not function. In the followingdescription and in the claims, the terms “include”, “comprise” and“have” are used in an open-ended fashion, and thus should be interpretedto mean “include, but not limited to . . . ”.

It will be understood that when an element or layer is referred to asbeing “disposed on” or “connected to” another element or layer, it canbe directly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent.

It should be noted that the technical features in different embodimentsdescribed in the following can be replaced, recombined, or mixed withone another to constitute another embodiment without departing from thespirit of the present disclosure.

FIG. 1 schematically illustrates a cross-sectional view of a displaydevice according to a first embodiment of the present disclosure. Thedisplay device DD1 is a flexible or foldable display device and includesa display panel DP1, a polarizer layer PL1, and a cover layer CL1, inwhich the polarizer layer PL1 is disposed on the display panel DP1, andthe cover layer CL1 is directly formed on the polarizer layer PL1.Specifically, the polarizer layer PL1 has a first surface S1 and asecond surface S2 opposite to each other, the cover layer CL1 isdirectly formed on the first surface S1, and the second surface S2 ofthe polarizer layer PL1 faces the display panel DP1. Since the coverlayer CL1 is directly formed on the polarizer layer PL1, extra layers,such as an adhesive layer for attaching the cover layer CL1 to thepolarizer layer PL1, can be not present between the polarizer layer PL1and the cover layer CL1. When a conventional display device is folded,stress will be generated. According to some embodiments, due to theabsence of the extra layers between the polarizer layer PL1 and thecover layer CL1, the stress between the extra layers and the stressesbetween the cover layer CL1 and the extra layers and between the extralayers and the polarizer layer PL1 can be prevented, thereby simplifyingthe stress between the cover layer CL1 and the polarizer layer PL1 andmitigating the stress between them.

In the present disclosure, the cover layer is “directly formed on” thepolarizer layer means that the cover layer is disposed on the polarizerlayer not by any adhesive. That is, there is no adhesive present betweenthe cover layer and the polarizer layer, and contact between the coverlayer and the polarizer layer is not by adhesion. For example, the firstsurface S1 of the polarizer layer PL1 is fully exposed before formingthe cover layer CL1, so when the cover layer CL1 is formed on the firstsurface S1, a surface of the cover layer CL1 facing the polarizer layerPL1 can be fully in contact with the first surface S1 of the polarizerlayer PL1. It should be understood that some undesired defects, such asvoids, may exist between the cover layer CL1 and the polarizer layerPL1, which may be generated during the manufacturing process of thecover layer CL1. This circumstance may still be interpreted as “thecover layer CL1 is directly formed on the polarizer layer PL1”.

In addition, the cover layer CL1 directly formed on the polarizer layerPL1 serves as an outmost layer of the display device DD1 for protectingthe elements in the display device DD1 from damage, breakage or scratch.In some embodiments, the cover layer CL1 can have a pencil hardnessgreater than or equal to 6H. To provide the display device DD1 withflexibility or foldability, the cover layer CL1 can have flexibility orfoldability. In some embodiments, the cover layer CL1 can be a polymer.For example, the cover layer CL1 is formed of organic hybrid resin,inorganic hybrid resin, acryl resin, polyimide, polycarbonate,poly(methyl methacrylate), polyethersulfone, polyamide, polyamide imide,polycarbonate poly(methyl methacrylate) copolymer, acrylic or siliconeresins or the like. The method for forming the cover layer CL1 on thepolarizer layer PL1 may for example include a coating method, aninjecting method, an inkjet printing method, or a deposition method, andis not limited. Also, a photolithography process and a UV curing methodcan be optionally performed.

The polarizer layer PL1 is configured to enhance the contrast ratio ofthe display device DD1 and is disposed on the display panel DP1 to coverthe display panel DP1. For example, the polarizer layer PL1 is used asan anti-reflection film for preventing ambient light from beingreflected by the display device DD1. In this embodiment, the polarizerlayer PL1 may include a linear polarizer LP1, a half wave film HW, and aquarter wave film QW, but not limited thereto. The quarter wave film QW,the half wave film HW and the linear polarizer LP1 can be stackedsequentially, and the half wave film HW and the quarter wave film QW aredisposed between the display panel DP1 and the linear polarizer LP1.Specifically, the first surface S1 is an outer surface of the linearpolarizer LP1, the second surface S2 is an outer surface of the quarterwave film QW, and the second surface S2 of the polarizer layer PL1 canbe adhered to the display panel DP1. In this embodiment, the displaydevice DD1 may further include an adhesive layer AL1 disposed betweenthe polarizer layer PL1 and the display panel DP1 for attaching thesecond surface S2 of the polarizer layer PL1 to the display panel DP1.In another embodiment, the polarizer layer PL1 may be composed of thelinear polarizer LP1, and has no half wave film HW and no quarter wavefilm QW, so the linear polarizer LP1 is directly attached to the displaypanel DP1 through the adhesive layer AL1.

In this embodiment, the polarizer layer PL1 has a first thickness T1 ina vertical direction Z, the cover layer CL1 has a second thickness T2 inthe vertical direction Z, and the first thickness T1 is greater than thesecond thickness T2. The vertical direction Z can be a thicknessdirection, and perpendicular to the first surface S1 of the polarizerlayer PL1. The polarizer layer PL1 can serve as a support substrate forsupporting the cover layer CL1 during formation of the cover layer CL1.Specifically, a ratio of the second thickness T2 to the first thicknessT1 can be in a range from 0.05 to 0.9. With such thickness ratio, when acombined body 10 including the polarizer layer PL1 and the cover layerCL1 is attached onto the display panel DP1 by the adhesive layer AL1,the cover layer CL1 is not easily damaged. Also, other yield problemsduring attaching may be prevented. For example, the second thickness T2of the cover layer CL1 may be in a range from 10 micrometers to 100micrometers or in a range from 20 micrometers to 80 micrometers, and thefirst thickness T1 of the polarizer layer PL1 may be in a range from 100micrometers to 200 micrometers or in a range from 150 micrometers to 190micrometers.

The display panel DP1 has a display surface DS and a back surface BSopposite to each other, and the display surface DS has a display regionDR for displaying images. The cover layer CL1 and the polarizer layerPL1 cover the display region DR. For example, the display panel DP1 maybe a flexible display panel or a foldable display panel, so the displaydevice DD1 can be flexible or foldable, and the display device DD1 canprovide portability when the display device DD1 is in a folded or bentstate. The flexible display panel or the foldable display panel may be aself-luminous display panel, such as an organic light-emitting diode(OLED) display panel, an inorganic light-emitting diode (LED) displaypanel or a quantum dot light-emitting diode (QLED) display panel, butnot limited herein. In this embodiment, the display panel DP1 mayinclude a supporting structure 20, a display layer DL, and anencapsulation layer EL. The supporting structure 20 is configured tosupport layers or films disposed thereon. The supporting structure 20can include a flexible substrate 20A and a supporting film 20B, and theflexible substrate 20A can be disposed on the supporting film 20B. Thedisplay layer DL is disposed on the supporting structure 20 fordisplaying images, for example the display layer DL may include drivingcircuits and display units. The driving circuits are for controlling thedisplay of display units, and the display units are for displayingdifferent color light. The driving circuits may for example includethin-film transistors, data lines, scan lines, power lines, and otherrequired elements, but not limited herein. The display units may forexample include inorganic light-emitting diodes, organic light-emittingdiodes or quantum dot light-emitting diodes. For inorganiclight-emitting diodes, each light-emitting diode (LED) may be a chipwith inorganic light emitting material for emitting light, for examplethe chip size of a mini-LED is in a range from 100 μm to 300 μm, or thechip size of a micro-LED is in a range from fpm to 100 μm. Those skilledin the art will understand that the display layer DL may further includeinsulation layers for insulating different elements and other requiredelements, and will not be detailed herein.

The encapsulation layer EL is disposed on the display layer DL andconfigured to encapsulate the display layer DL on the supportingstructure 20, so as to prevent the display layer DL from damage byoxygen and moisture or other damage during manufacturing processes orduring use. The encapsulation layer EL may include a flexibleencapsulation material, which includes an inorganic material, an organicmaterial, or a combination thereof. For example, the inorganic materialmay be for example aluminum oxide, silicon nitride, silicon oxynitride,or diamond-like carbon, and the organic material may be UV-curableadhesive, polymethyl methacrylate, polyimide, parylene, polyacrylate oracrylate monomer. In this embodiment, the display panel DP1 may be a topemission display panel, but not limited thereto. In another embodiment,the display panel DP1 may be a double-emission display panel or abottom-emission display panel.

The display panel DP1 has a third thickness T3 in the vertical directionZ. The third thickness T3 may be measured from an outer surface of theencapsulation layer EL (that is the display surface DS) to a bottomsurface of the display panel DP1 (that is the back surface BS). Thebottom surface of the display panel DP1 is the bottom surface of thesupporting film 20B of the supporting substrate 20.

Specifically, refer to FIG. 2 , which schematically illustrates thedisplay device in a folded state. The display device is folded such thattwo portions of a cover surface 12S of the cover layer CL1 face eachother, which can be referred to as folded inwardly. In otherembodiments, although not shown, the display device can also be foldedoutwardly, such that two portions of the back surface BS of the displaypanel DP1 face each other. The term “folded” in the present disclosuremeans curved, bent, folded, rolled, stretched, flexed, or the like(generally referred to as “folded” or “foldable” hereinafter).

According to some embodiments, a ratio of the third thickness T3 to asum of the first thickness T1 and the second thickness T2 can be in arange from 0.8 to 1.2. Through the thickness ratio design, the stress tothe polarizer layer PL1 and the cover layer CL1 and the stress to thedisplay panel DP1 may be balanced, and damages to the display device DD1during folding or bending may be minimized. Thus, crack on the coverlayer CL1, the layers (such as circuits) of the display panel DP1, orother layers in the display device DD1 can be prevented or mitigated.For example, the first thickness T1 may be 100 micrometers, the secondthickness T2 may be 60 micrometers, and the third thickness T3 may be150 micrometers, but not limited herein.

In some embodiments, an area of the polarizer layer PL1 can be equal toor greater than an area of the display panel DP1. For example, referringto FIG. 1 , a first distance F1 between an edge 31 of the display panelDP1 and an edge 32 of the polarizer layer PL1 can be in a range from 0to 5 millimeters. When the area of the of the polarizer layer PL1 isgreater than the area of the display panel DP1, the first distance F1can be greater than 0, for example, in a range from 0.1 to 5millimeters.

In this embodiment, the display device DD1 may be for example formed bythe following description. First, referring to FIG. 1 , a flexiblesubstrate 20A is formed on a rigid substrate (not shown), and followedby forming the display layer DL on the flexible substrate 20A. The rigidsubstrate may be for example a glass substrate. The encapsulation layerEL is then formed to cover and encapsulate the display layer DL. Afterthe encapsulation layer EL is formed, the rigid substrate is removed toexpose the flexible substrate 20A. Then, a supporting film 20B isadhered to the flexible substrate 20A through an adhesive (not shown).Accordingly, the display panel DP1 is formed. Also, the flexiblesubstrate 20A and the supporting film 20B may constitute the supportingstructure 20 for supporting the display layer DL and the encapsulationlayer EL. The flexible substrate 20A and the supporting film 20B may beformed of any insulating material that is flexible. For example, theinsulating material may include polyethylene terephthalate (PET),polyimide (PI), or polyethylene naphthalate (PEN), but not limitedthereto.

Refer to FIG. 3 as well as FIG. 1 . FIG. 3 schematically illustrates amethod of forming the cover layer CL1. First, a cover structure (notshown) is formed by coating on a polarizer mother layer PML. Then, thecover structure is patterned by photolithography to form a plurality ofcover layers CL1. The cover layers CL1 may be formed and separated fromeach other, and two adjacent cover layers CL1 can be separated by aspacing SP. Thereafter, the polarizer mother layer PML is cut alongcutting lines CU. Thus, a plurality of the combined bodies 10 areseparated. Each individual combined body 10 includes one polarizer layerPL1 and one cover layer CL1. Then, the combined body 10 can be attachedonto the display panel DP1 by the adhesive layer AL1 to form the displaydevice DD1 as shown in FIG. 1 and as mentioned above.

In some embodiments, due to the design of the spacing SP between thecover layers CL1, when the polarizer mother layer PML is cut, the coverlayers CL1 will not be cut. Thus, no crack would be generated in thecover layer CL1, so an optical function of the cover layer CL1, such astransparency, would not be affected by the cutting process, or crack onthe cover layer CL1 can be mitigated. In some embodiments, in order notto cut the cover layer CL1, the spacing SP may be greater than a widthof the cutting line CU. For example, the spacing SP can be in a rangefrom 0 to 40 micrometers, for example, in a range from 2 to 30micrometers. The spacing SP can be greater than 0.

Referring to FIG. 1 and FIG. 3 , after the polarizer mother layer PML iscut, and a plurality of the combined bodies 10 are formed. For oneindividual combined body 10, the edge of the cover layer CL1 is disposedinwardly than the edge of the polarizer layer PL1. Specifically, an edge33 of the cover layer CL1 is spaced apart from and disposed inwardlythan the edge 32 of the polarizer layer PL1 by a second distance F2,which may be called a buffer region. The distance F2 may be in a rangefrom 0 to 20 micrometers, for example, in a range from 1 micrometer to15 micrometers. Specifically, another edge 33 a of the cover layer CL1can be spaced apart from another edge 32 a of the polarizer layer PL1.In some embodiments, each edge of each cover layer CL1 is spaced apartfrom a corresponding edge of the polarizer layer PL1 respectively, sothe buffer regions can surround the cover layer CL1, but not limitedthereto.

Alternatively, in other embodiments, first, a cover structure (notshown) is formed by coating on a polarizer mother layer PML. The coverstructure can be not subjected to patterning, and the plurality of coverlayers CL1 can be continuous and in an integral structure on thepolarizer mother layer PML. That is, no spacing SP is present betweentwo adjacent cover layers CL1. Then, the polarizer mother layer PML andthe cover structure are cut along the cutting lines CU, and a pluralityof combined bodies 10 are formed. Thus, in the individual combined body10, at least two adjacent edges of the cover layer CL1 can be aligned tothe corresponding two edges of the polarizer layer PL1. For example,referring to FIG. 3 , in the combined body 10, the edges 33 and 33 a ofthe cover layer CL1 can be aligned to the corresponding edges 32 and 32a of the polarizer layer PL1, respectively.

In some embodiments, the cover structure can be formed such that an edge330 of the cover structure is spaced apart from the corresponding edge320 of the polarizer mother PML, as shown in FIG. 3 . Thus, at least oneedge of the cover layer CL1 may be spaced apart from the correspondingedge of the polarizer PL1 (which is a part of the edge of the polarizermother layer PML). For example, at least one edge of the cover layerCL1, such as the edge 33 b, may be spaced apart from the correspondingedge of the polarizer layer PL1, such as the edge 32 b, and at least twoadjacent edges of the cover layer CL1, such as the edge 33 and the edge33 a, may be respectively aligned to at least two adjacent edges of thepolarizer layer PL1, such as the edge 32 and the edge 32 a. Or,alternatively, in other embodiments, the cover structure can be formedsuch that an edge 330 of the cover structure is aligned to thecorresponding edge 320 of the polarizer mother PML, not shown.

According to some embodiments, the display panel can further include atouch layer to provide the touch function, thus forming a touch displaypanel. For example, referring to FIG. 1 , the display panel DP1 of thisembodiment may selectively further include a touch layer TL between theencapsulation layer EL and the adhesive layer AL1 for touch sensing.FIG. 1 shows that the touch layer TL is directly formed on theencapsulation layer EL, and the touch display panel is so-called on-celltype display panel. Since a thickness of the touch layer TL is much lessthan the third thickness T3 of the display panel DP1, the disposition ofthe touch layer TL may not affect the folding or bending of the displaydevice DD1. Accordingly, the third thickness T3 is still defined from anouter surface of the encapsulation layer EL (that is the display surfaceDS) to a bottom surface of the display panel DP1 (that is the backsurface BS) when the display panel DP1 includes the touch layer TL. Inanother embodiment (not shown), the touch layer TL may be disposedbetween the encapsulation layer EL and the supporting substrate 20, sothe display panel DP1 is so-called in-cell type display panel. Infurther another embodiment (not shown), the touch layer TL may be formedon a film and followed by being adhered to the encapsulation layer ELthrough another adhesive, so the display panel DP1 is so-called out-celltype display device.

According to some embodiments, the display device can be foldable. FIG.1 shows the display device DD1 in an un-folded state, and FIG. 2 showsthe display device DD1 in a folded state. The display device DD1 mayhave a main region R1 and a foldable region R2. In other words, theflexibility of the display device DD1 in the foldable region R2 isgreater than the flexibility of the display device DD1 in the mainregion R1, so the display device DD1 in the foldable region R2 may serveas a foldable portion that is capable of being folded. Specifically, thedisplay device DD1 may further have another main region R1, and thefoldable region R2 is disposed between the two main regions R1.According to some embodiments, the cover layer in the foldable region R2may include recess portions. For example, the cover layer CL2 has aplurality of first recess portions 51 in the foldable region R2 as shownin following FIG. 4 and FIG. 5 , which can increase flexibility of thefoldable region R2, but not limited thereto. In another embodiment, asshown in FIG. 1 , the cover layer CL1 in the foldable region R2 may nothave the first recess portions.

According to some embodiments, referring to FIG. 1 , the adhesive layerAL1 of this embodiment may selectively include two first adhesive partsALa and a second adhesive part ALb, in which the first adhesive partsALa are disposed in the main regions R1, and the second adhesive partALb is disposed in the foldable region R2. In order to enhancefoldability in the foldable region R2 and differentiate the flexibilityin the main regions R1 from the flexibility in the foldable region R2, aYoung's modulus of the second adhesive part ALb can be less than aYoung's modulus of each first adhesive part ALa. Accordingly, the secondadhesive part ALb is more elastic than each first adhesive part ALa. TheYoung's modulus described herein is defined as the Young's modulus ofthe adhesive layer AL1 after being cured. In another embodiment, theadhesive layer AL1 may be composed of one layer that has uniform Young'smodulus.

In addition, in some embodiments, the supporting substrate 20 caninclude a second recess portion 52 in the foldable region R2, as shownin FIG. 1 . The second recess portion 52 can be on a surface away fromthe display layer DL, for example, on the back surface BS of the displaypanel DP1. Although not shown, the second recess portion 52 can be morethan one, for example, plural, according to requirements. Due to thesecond recess portion 52, the stress to the display panel DP1 in thefoldable region R2 can be mitigated. In some embodiments, the secondrecess portion 52 may penetrate through the supporting film 20B andexpose the surface of the flexible substrate 20A, as shown in FIG. 1 .Alternatively, in some embodiments, although not shown in figures, thesecond recess portion 52 may not penetrate through the supporting film20B, and a portion of the supporting film 20B remains in the positioncorresponding to the second recess portion 52. In some embodiments, thesupporting substrate 20 may not have the second recess portion 52.

The display device of the present disclosure is not limited to the aboveembodiment. Further embodiments of the present disclosure are describedbelow. To compare the embodiments conveniently and simplify thedescription, the same component would be labeled with the same symbol inthe following. The following description will detail the dissimilaritiesamong different embodiments and the identical features will not beredundantly described.

FIG. 4 schematically illustrates a top view of a display deviceaccording to a second embodiment of the present disclosure, and FIG. 5schematically illustrates a cross-sectional view of the display devicetaken along a cross-sectional line A-A′ of FIG. 4 . A main differencebetween the display device DD2 of this embodiment and the display deviceDD1 of the first embodiment as shown in FIG. 1 is the design of thecover layer. In FIG. 4 and FIG. 5 , the cover layer CL2 includes a firstsub-layer CLa, and the first sub-layer CLa includes a plurality of firstrecess portions 51 in the foldable region R2. Each first recess portion51 may be a through hole penetrating through the first sub-layer CLa andexpose the surface of the polarizer layer PL1, as shown in FIG. 5 . Or,alternatively, in some embodiments, the first recess portions 51 may notpenetrate through the first sub-layer CLa, and a portion of the firstsub-layer CLa remains in the position corresponding to the first recessportions 51. Specifically, the first sub-layer CLa includes two mainparts MP in the main regions R1 and a patterned part PP in the foldableregion R2. The two main parts MP can be connected by the patterned partsPP to form an integral portion, and the patterned part PP can surroundthe first recess portions 51. Through the first recess portions 51, theflexibility of the display device DD2 in the foldable region R2 can begreater than the flexibility of the display device DD2 in the mainregions R1. In this embodiment, the first sub-layer CLa has two mainparts MP disposed in the main regions R1 respectively, but not limitedthereto. In another embodiment, at least one of the main parts MP of thefirst sub-layer CLa may have first recess portions 51.

For easy illustration, FIG. 4 and FIG. 5 shows that the edges of displaypanel DP2, the polarizer layer PL1, and the cover layer CL2 are aligned.However, in some embodiments, the edges of display panel DP2, thepolarizer layer PL1, and the cover layer CL2 can be not aligned, asshown in FIG. 1 . That is, in the display device DD2, the edge of thedisplay panel DP2 and the edge of the polarizer layer PL1 can be spacedapart by a first distance F1, and the edge of the polarizer layer PL1and the edge of the cover layer CL2 can be spaced apart by a seconddistance F2, as mentioned in the previous embodiments. Similarly, in thefollowing embodiments, the edges of display panel, the polarizer layer,and the over layer can be aligned as shown in the following figures foreasy illustration. Alternatively, the edges of display panel, thepolarizer layer, and the cover layer can be not aligned, and the displaydevices in the following embodiments can have the design of the firstdistance F1 and the second distance F2, as mentioned above. Also, in theprocedure of cutting the polarizer mother layer, the buffer regiondesign for the cover layer as mentioned above can be performed in thefollowing embodiments.

In some embodiments, the arrangement of the first recess portions 51 maybe for example a matrix arrangement, a brick arrangement or othersuitable arrangement. The shape of one of the first recess portions 51may be for example rectangular, hexagonal or other suitable shapes.Also, referring to FIG. 4 , a width W1 of each first recess portion 51in a first direction D1 may be equal to or less than 20 micrometers, anda width W2 of each first recess portion 51 in a second direction D2 mayalso be equal to or less than 20 micrometers. Since the widths W1 and W2are equal to or less than 20 micrometers, the first recess portions 51would not be easily seen during use, thereby mitigating visibility ofthe first recess portions 51 and maintaining image quality.

Furthermore, in some embodiments, the profile of the patterned part PPof the first sub-layer CLa in the foldable region R2 can have a curvedshape. Specifically, referring to FIG. 5 , the patterned part PPincludes a plurality of projections 5P. Two adjacent projections 5P areseparated by one of the first recess portions 51. Atop surface 5T of theprojection 5P connects to a sidewall 5S of the first recess portion 51by a corner IE, and the profile of the corner IE has a curved shape, forexample, a rounded shape. Since the first sub-layer CLa is the outmostlayer of the display device DD2, through the curved corner design, thefirst sub-layer CLa can be prevented from damage resulted fromscratching or hitting during use. In another embodiment, the corners IEof the patterned part PP abutting the first recess portions 51 may haveright-angled corners. In some embodiments, the top surface 5T of theprojection 5P can have a curved shape.

Referring to FIG. 5 , the adhesive layer AL2 of this embodiment may becomposed of one layer that has single Young's modulus. In anotherembodiment, the adhesive layer AL2 may be the same as the adhesive layerAL1 of the first embodiment. That is, the adhesive layer AL2 can have afirst adhesive layer in the main region R1 and a second adhesive layerin the foldable region R2, and the first adhesive layer and the secondadhesive layer can have different Young's moduli. FIG. 5 shows that thedisplay panel DP2 does not include the second recess portion. However,alternatively, in some embodiments, the display panel DP2 can includethe second recess portion, similar to the second recess portion 52disposed in the supporting film 20B as shown in FIG. 1 , and detaileddescription is omitted here for brevity.

FIG. 6 schematically illustrates a display device according to a thirdembodiment of the present disclosure. A difference between the displaydevice DD3 of this embodiment and the display device DD2 of the secondembodiment shown in FIG. 4 is the design of the cover layer. In FIG. 6 ,the cover layer CL3 of this embodiment further includes a secondsub-layer CLb disposed in the foldable region R2, and the firstsub-layer CLa and the second sub-layer CLb have different Young'smoduli. In this embodiment, a Young's modulus of the second sub-layerCLb is less than a Young's modulus of the first sub-layer CLa, so thatthe second sub-layer CLb can be more elastic than the first sub-layerCLa, and the display device DD3 in the foldable region R2 may providelarger flexibility than the display device DD3 in each main region R1.At least a portion of the second sub-layer CLb is filled in the firstrecess portions 51 of the first sub-layer CLa. In this embodiment, thesecond sub-layer CLb may cover the patterned part PP of the firstsub-layer CLa. A part of the second sub-layer CLb may further extendinto the main regions R1, but not limited thereto. Furthermore, a ratioof the Young's modulus of the first sub-layer CLa to the Young's modulusof the second sub-layer CLb is in a range from 2 to 20, so as to balancethe stress between the first sub-layer CLa and the second sub-layer CLb.In this embodiment, the adhesive layer AL3 and the display panel DP3 maybe the same as or similar to the above-mentioned adhesive layers and thedisplay panels, and detailed descriptions are omitted.

FIG. 7 schematically illustrates a display device according to a fourthembodiment of the present disclosure. A difference between the displaydevice DD4 of this embodiment and the display device DD3 of the thirdembodiment shown in FIG. 6 is the design of the cover layer. In FIG. 7 ,the first sub-layer CLa is only disposed in the main regions R1, and thesecond sub-layer CLb is disposed in the foldable region R2 and coversthe foldable region R2. In this embodiment, the first sub-layer CLa onlyhas the main parts MP in the main regions R1 respectively, but notlimited thereto. In some embodiments, the first sub-layer CLa and thesecond sub-layer CLb can have different Young's moduli. FIG. 7 showsthat the first sub-layer CLa in the main region R1 has no recessportion, and the second sub-layer CLb in the foldable region R2 has norecess portion. However, in another embodiment, at least one of the mainparts MP of the first sub-layer CLa in the main regions R1 may havepatterned structure. In this embodiment, the adhesive layer AL4 and thedisplay panel DP4 may be the same as or similar to the above-mentionedadhesive layers and the display panels, and detailed descriptions areomitted.

FIG. 8 schematically illustrates a display device according to a fifthembodiment of the present disclosure. A difference between the displaydevice DD5 of this embodiment and the display device DD4 of the fourthembodiment shown in FIG. 7 is the design of the cover layer. In FIG. 8 ,the second sub-layer CLb includes a plurality of third recess portions53. Specifically, the second sub-layer CLb includes a plurality ofprotrusions PR separated from each other, and the third recess portion53 is disposed between any two of the adjacent protrusions PR. Eachthird recess portion 53 may be a through hole penetrating through thesecond sub-layer CLb and expose the surface of the polarizer layer PL1,as shown in FIG. 8 . Or, alternatively, in some embodiments, the thirdrecess portions 53 may not penetrate through the second sub-layer CLb,and portions of the second sub-layer CLb can remain in the positioncorresponding to the third recess portions 53. For example, a width ofeach third recess portion 53 may be equal to or less than 20micrometers. In this embodiment, the first sub-layer CLa further extendsinto the foldable region R2, and at least a portion of the firstsub-layer CLa is filled in the third recess portions 53. The firstsub-layer CLa may further cover the second sub-layer CLb. The presentdisclosure is not limited thereto. In another embodiment, the firstsub-layer CLa may not extend into the foldable region R2. In thisembodiment, the adhesive layer AL5 and the display panel DP5 may be thesame as or similar to the above-mentioned adhesive layers and thedisplay panels, and detailed descriptions are omitted.

FIG. 9 schematically illustrates a display device according to a sixthembodiment of the present disclosure. A main difference between thedisplay device DD6 of this embodiment and the display device DD1 of thefirst embodiment shown in FIG. 1 is the surface roughness of the coverlayer. In FIG. 9 , the cover layer CL6 of this embodiment has a coversurface 60S away from the polarizer layer PL1, the cover surface 60S hastwo first parts 61 respectively in the main regions R1, and a secondpart 62 in the foldable region R2. A roughness of the second part 62 ofthe cover surface 60S in the foldable region R2 can be greater than aroughness of the first part 61 of the cover surface 60S in the mainregion R1. The difference between the roughness of the first part 61 andthe roughness of the second part 62 may be achieved for example by anetching process, but not limited thereto. Through the roughnessdifference, elasticity of the display device DD6 in the foldable regionR2 can be greater than that in the main regions R1. In this embodiment,the cover layer CL6 may be formed of the same material, but not limitedthereto. In another embodiment, the cover layer CL6 may include a firstsub-layer and a second sub-layer, the first sub-layer can include thefirst parts 61, and the second sub-layer can include the second part 62.In this embodiment, the adhesive layer AL6 and the display panel DP6 maybe the same as or similar to the above-mentioned adhesive layers and thedisplay panels, and detailed descriptions are omitted.

FIG. 10 schematically illustrates a display device according to aseventh embodiment of the present disclosure. A main difference betweenthe display device DD7 of this embodiment and the display device DD1 ofthe first embodiment shown in FIG. 1 is that the cover layer CL7 isdisposed in the foldable region R2, and the display device DD7 furtherincludes a cover plate 70 and another adhesive layer AAL between thecover plate 70 and the polarizer layer PL1. Specifically, the displaydevice DD7 includes two cover plates 70 and two adhesive layers AAL, inwhich each adhesive layer AAL attach each cover plate 70 to thepolarizer layer PL1. Also, each cover plate 70 and each adhesive layerAAL are disposed in each main region R1 respectively. A Young's modulusof the cover plate 70 can be greater than a Young's modulus of the coverlayer CL7. For example, each cover plate 70 may be formed of a rigidsubstrate, such as a glass substrate. In this embodiment, the adhesivelayer AL7 and the display panel DP7 may be the same as or similar to theabove-mentioned adhesive layers and the display panels, and detaileddescriptions are omitted.

FIG. 11 schematically illustrates a display device according to aneighth embodiment of the present disclosure. A difference between thedisplay device DD8 of this embodiment and the display device DD1 of thefirst embodiment shown in FIG. 1 is design of the polarizer. In FIG. 11, the polarizer layer PL8 includes a fourth recess portion 54.Specifically, the polarizer layer PL8 can include a linear polarizerLP8, and the linear polarizer LP8 can include a first protection layer81, a second protection layer 83, and a linear polarizer material 82disposed between the first protection layer 81 and the second protectionlayer 83. In some embodiments, the polarizer layer PL8 may include ahalf-wave film HW and a quarter-wave film QW, disposed under the linearpolarizer LP8. Referring to FIG. 11 , the first protection layer 81 caninclude the plurality of fourth recess portions 54 in the foldableregion R2. Also, the fourth recess portions 54 is disposed on the firstsurface 80 of the polarizer layer PL8, which contacts the cover layerCL8, and a portion of the cover layer CL8 is filled in the fourth recessportions 54. Through the fourth recess portions 54, elasticity of thedisplay device DD8 in the foldable region R2 can be greater thanelasticity of the display device DD8 in the main regions R1. In someembodiments, each fourth recess portion 54 may be a through holepenetrating through the first protection layer 81 and expose the surfaceof the linear polarizer material 82, not shown in figures. Or,alternatively, in some embodiments, as shown in FIG. 8 , the fourthrecess portions 54 may not penetrate through the first protection layer81, and a portion of the first protection layer 81 remains in theposition corresponding to the fourth recess portions 54. In thisembodiment, the adhesive layer AL8 and the display panel DP8 may be thesame as or similar to the above-mentioned adhesive layers and thedisplay panels, and detailed descriptions are omitted. Each of the firstprotection layer 81 and the second protection layer 83 can be, forexample, a triacetyl cellulose (TAC) film, and the linear polarizermaterial 82 can be, for example, made of polyvinyl alcohol (PVA).

FIG. 12 schematically illustrates a display device according to a ninthembodiment of the present disclosure. A difference between the displaydevice DD9 of this embodiment and the display device DD8 of the eighthembodiment shown in FIG. 11 is that the polarizer layer PL9 includesrecess portions on two surfaces in the foldable region R2. Referring toFIG. 12 , the polarizer layer PL9 includes a plurality of fourth recessportions 54 a on the first surface 80 a and a plurality of fifth recessportions 54 b on the second surface 80 b. Specifically, the fourthrecess portions 54 a are disposed on the first surface 80 a of the firstprotection layer 81 in the foldable region R2, and the fifth recessportions 54 b are disposed on the second surface 80 b of the secondprotection layer 83 in the foldable region R2. In some embodiments, thefourth recess portions 54 a can be filled with the cover layer CL9.Specifically, the polarizer layer PL9 of this embodiment may not includethe half-wave film HW and the quarter-wave film QW, so the secondprotection layer 83 may contact the adhesive layer AL9, and the fifthrecess portions 54 b can be filled with the adhesive layer AL9. Throughthe fourth recess portions 54 a and the fifth recess portions 54 b,elasticity of the display device DD9 in the foldable region R2 can bemuch greater than elasticity of the display device DD9 in the mainregions R1. In this embodiment, the adhesive layer AL9 and the displaypanel DP9 may be the same as or similar to the above-mentioned adhesivelayers and the display panels, and detailed descriptions are omitted.

As the mentioned above, according to some embodiments, in the displaydevice of the present disclosure, since the cover layer is directlyformed on the polarizer layer, no extra layer exists between the coverlayer and the polarizer layer, thereby reducing the number of the layersin the display device. Accordingly, in some embodiments, the stressbetween the cover layer and the polarizer layer can be simplified andmitigated. In some embodiments, by means of the design of the coverlayer, recess portions, Young's modulus adjustment, and/or surfaceroughness of the cover layer, the display device can be suitable for useas a foldable display device, and crack occurring during folding can beprevented or mitigated.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the disclosure. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A display device comprising: a display panelhaving a substrate with two opposite first edges; an optical layerdisposed on the display panel, the optical layer having two oppositesecond edges corresponding to the two opposite first edges respectively;and a cover layer disposed on the optical layer, wherein one of the twoopposite first edges and one of the two opposite second edgescorresponding to the one of the two opposite first edges are notaligned.
 2. The display device as claimed in claim 1, wherein theoptical layer comprises a polarizer layer.
 3. The display device asclaimed in claim 1, wherein a first thickness of the optical layer isdifferent from a second thickness of the cover layer.
 4. The displaydevice as claimed in claim 3, wherein the second thickness is less thanthe first thickness.
 5. The display device as claimed in claim 4,wherein a ratio of the second thickness to the first thickness is in arange from 0.05 to 0.9.
 6. The display device as claimed in claim 4,wherein the display panel has a third thickness, and a ratio of thethird thickness to a sum of the first thickness and the second thicknessis in a range from 0.8 to 1.2.
 7. The display device as claimed in claim1, wherein the cover layer comprises a polymer.
 8. The display device asclaimed in claim 1, further comprising an adhesive layer attachedbetween the optical layer and the display panel.
 9. The display deviceas claimed in claim 1, wherein the display panel comprises a displaylayer.
 10. The display device as claimed in claim 9, wherein the displaypanel comprises an encapsulation layer disposed on the display layer.11. The display device as claimed in claim 10, wherein the display panelcomprises a touch layer disposed on the encapsulation layer.
 12. Thedisplay device as claimed in claim 9, wherein the display layercomprises a plurality of organic light-emitting diodes.